Hydraulic elevators employ the use of a long piston or plunger rod which supports the car of the elevator for movement through the elevator shaft. The piston or plunger is hydraulically actuated to move the car to the desired elevation. As the piston moves through an associated supporting cylinder, it passes through a sealed stuffing box at the mouth of the cylinder. To facilitate the movement of the piston or plunger rod through the stuffing box, a lubricant, such as grease, is placed in the stuffing box. As the elevator is used, the movement of the piston through the stuffing box causes the grease to get hot and the surface area of rubber seals in the stuffing box to peel off. Once the surface of the seal has peeled, the hot grease penetrates the rubber of the seal causing the seal to stick and grab the piston as it moves through the stuffing box. This phenomenon is experienced by the elevator passenger as unsettling moaning and squealing noises and jerky movement of the elevator as it travels between floors.
Noise and rough, jerky rides may also be the result of a properly functioning seal in the stuffing box. Where the stuffing box utilizes dual seals, the top seal will dry out when the lower seal is properly preventing hydraulic fluid in the cylinder from entering the stuffing box, keeping the piston dry above the lower seal. Thus, the piston does not carry spent oil or other hydraulic fluid to the upper seal, thereby allowing the upper seal to dry out. As the dry piston moves against the surface of the dry seal, the friction generates the vibration and noises experienced by the passengers. In either event, if the seals and piston are not properly lubricated, the seals deteriorate rapidly and must be frequently replaced.
Historically oil or grease has been manually applied to the exterior of the piston by an elevator workman to reduce the noise, ensure smoother movement of the piston through the stuffing box, and increase the life of the seals. The process is extremely burdensome, requiring that the elevator be taken out of service while the piston is lubricated, and is often ineffective. Additionally, the manual process must be repeated often increasing time and costs associated with maintenance of the elevator.
To overcome these problems, there have been attempts in the hydraulic elevator industry to recirculate spent oil to a reservoir surrounding and in contact with the piston surface for reapplying the oil to the piston. Such attempts have proven ineffective, inefficient, not to mention messy, and still require frequent maintenance to insure sufficient and even lubrication of the piston.